Introduction of powered relay for device-to-device communication

ABSTRACT

Methods, systems, and devices are described for wireless communication. Device-to-device (D2D) communications may benefit from the use of a relay facilitating communications between mobile devices. Relays which are not power-limited, such as if the relay is connected to a power grid, may continuously monitor the communication medium. A relay may monitor D2D communications and determine a D2D pair for which to attempt to facilitate communications. The relay may identify a first message from a first mobile device to a second mobile device, and may transmit a second message to the second mobile device. The second message may be transmitted using the same resources as the first message, and may include at least a portion of the first message. The relay may receive a response from the second mobile device and may transmit information about the relay to the second device before facilitating communications between the D2D pair of mobile devices.

BACKGROUND

1. Field of the Disclosure

The following relates generally to wireless communication, and morespecifically to introduction of powered relay for device-to-device (D2D)communication.

2. Description of Related Art

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems, (e.g., a Long Term Evolution(LTE) system). A wireless multiple-access communications system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple communication devices, which may be otherwiseknown as user equipment (UE). A wireless multiple-access communicationsystem may also, or alternatively, support D2D communication betweencommunication devices (e.g., between UEs). D2D communications mayinvolve wireless communications directly between communication devices(e.g., directly between UEs, without the communications passing throughone or more base stations).

D2D communications may sometimes be relayed through one or moreintermediary communication devices (e.g., through one or more relays). Arelay may take the form of a dedicated relay device or be part ofanother device, such as a base station or UE. A relay may be an idlemobile device that happens to be in the vicinity of the D2D link.Conserving battery power for the relay may be desired, and may result intwo distinct time periods, a relay selection period and a datacommunication period. The two time periods may be periodic and repeatone after another. The time used for the relay selection period may beshort to reduce the overhead associated with determining relaycandidates. Further, to reduce power consumption at the relay, the relayselection period may occur infrequently. However, it may be desired toestablish a method of communication with a relay which does not need toadhere to the same power requirements as other relays.

SUMMARY

Systems, methods, and apparatuses for introduction of powered relay fordevice-to-device (D2D) communication are described. A relay may identifya set of D2D messages associated with a set of D2D device pairs. Therelay may identify a first message transmitted from a first devicedirected to a second device using D2D communications on a first set ofresources. The relay may attempt to facilitate communications betweenthe first device and the second device based on the first message, orthe set of D2D messages, or a combination thereof. The relay maytransmit a second message to the second device on the first set ofresources upon identifying the transmission of the first message, thesecond message may include at least a portion of the first message. Therelay may receive a response to the second message from the seconddevice. The relay may transmit information associated with the relaydevice to the second device, the information may include anidentification of the relay device, or a modulation and coding scheme(MCS), or a combination thereof. The relay may further facilitatecommunications between the first device and the second device.

A method of wireless communication is described. The method may includeidentifying, at a relay device, a first message transmitted from a firstdevice directed to a second device using D2D communications on a firstset of resources, transmitting a second message to the second device onthe first set of resources upon identifying the transmission of thefirst message, the second message comprising at least a portion of thefirst message, and receiving a response to the second message from thesecond device.

An apparatus for wireless communication is described. The apparatus mayinclude means for identifying, at a relay device, a first messagetransmitted from a first device directed to a second device using D2Dcommunications on a first set of resources, means for transmitting asecond message to the second device on the first set of resources uponidentifying the transmission of the first message, the second messagecomprising at least a portion of the first message, and means forreceiving a response to the second message from the second device.

A further apparatus for wireless communication is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory and operable,when executed by the processor, to cause the apparatus to identify, at arelay device, a first message transmitted from a first device directedto a second device using D2D communications on a first set of resources,transmit a second message to the second device on the first set ofresources upon identifying the transmission of the first message, thesecond message comprising at least a portion of the first message, andreceive a response to the second message from the second device.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableto identify, at a relay device, a first message transmitted from a firstdevice directed to a second device using D2D communications on a firstset of resources, transmit a second message to the second device on thefirst set of resources upon identifying the transmission of the firstmessage, the second message comprising at least a portion of the firstmessage, and receive a response to the second message from the seconddevice.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for transmitting the second message tothe second device at a power level that is equal to a power level usedto transmit the first message to the second device. Additionally oralternatively, some examples may include processes, features, means, orinstructions for facilitating communications between the first deviceand the second device.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, facilitating communicationscomprises at least one of receiving a third message from the firstdevice and retransmitting the third message to the second device, andreceiving a fourth message from the second device and retransmitting thefourth message to the first device. Additionally or alternatively, someexamples may include processes, features, means, or instructions wherefacilitating communications between the first device and the seconddevice is initiated by the relay device.

Some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein may further include processes,features, means, or instructions for identifying, at the relay device, aplurality of D2D messages associated with a plurality of D2D devicepairs, and attempting to facilitate communications between the firstdevice and the second device based at least in part on the firstmessage, or the plurality of D2D messages, or a combination thereof.Additionally or alternatively, some examples may include processes,features, means, or instructions for transmitting information associatedwith the relay device to the second device, the information comprisingan identification of the relay device, or a modulation and coding scheme(MCS), or a combination thereof.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the relay device is connectedto a power grid. Additionally or alternatively, in some examples a D2Dcommunication link is established between the first device and thesecond device.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the first message is arequest-to-send (RTS) message. Additionally or alternatively, in someexamples the response is a clear-to-send (CTS) message.

In some examples of the method, apparatuses, or non-transitorycomputer-readable medium described herein, the response is anacknowledgment (ACK). Additionally or alternatively, in some examplesthe first set of resources comprises a frequency channel, or a timeslot, or a coding rate, or an MCS, or a combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure are described in reference to the followingfigures:

FIG. 1 illustrates an example of a wireless communications system thatsupports introduction of powered relay for device-to-device (D2D)communication in accordance with various aspects of the presentdisclosure;

FIG. 2 illustrates an example of a wireless communications subsystemthat supports introduction of powered relay for D2D communication inaccordance with various aspects of the present disclosure;

FIG. 3 illustrates an example of a process flow that supportsintroduction of powered relay for D2D communication in accordance withvarious aspects of the present disclosure;

FIGS. 4-6 show block diagrams of a wireless device that supportsintroduction of powered relay for D2D communication in accordance withvarious aspects of the present disclosure;

FIG. 7 illustrates a block diagram of a system including a userequipment (UE) that supports introduction of powered relay for D2Dcommunication in accordance with various aspects of the presentdisclosure; and

FIGS. 8-11 illustrate methods for introduction of powered relay for D2Dcommunication in accordance with various aspects of the presentdisclosure.

DETAILED DESCRIPTION

A relay, such as a power-grid-connected (PGC) relay, may not adhere tothe same power requirements as a battery operated relay. As such, therelay may always be on, and may constantly monitor the medium. Byconstantly monitoring the medium, the relay may reduce or remove thechannel measurement phase of the relay selection period. Further, it maybe desired for the relay to enhance a device-to-device (D2D)communication link at any point in time, rather than waiting for therelay selection period. By enhancing the D2D communication link,whenever the relay is able to do so, latency may be greatly reduced.Additionally, while battery powered relays may enhance D2D communicationlinks, the battery powered relays may need to be initiated by thetransmitter or receiver in the D2D link, so as to limit powerconsumption of the potentially large number of relay candidates.

When using a relay, such as a PGC relay, not only may the relayconstantly monitor the medium, but the relay may initiate enhancement ofthe D2D link without compromising battery power. In fact, the relay mayreduce power consumption at the D2D devices by initiating relayfunctionality. A relay may monitor communications in its vicinity. Forexample, the relay may monitor request-to-send (RTS), clear-to-send(CTS), acknowledgment (ACK), or negative acknowledgment (NACK) messages.By monitoring communications, the relay may determine a D2D pair whichit could help with communications. Further, if there are multiple D2Dpairs in vicinity of the relay, the relay may determine which D2D paircould benefit the most from its assistance.

Aspects of the disclosure are initially described in the context of awireless communication system. Specific examples are then described forD2D communications. These and other aspects of the disclosure arefurther illustrated by and described with reference to apparatusdiagrams, system diagrams, and flowcharts that relate to introduction ofpowered relay for D2D communication.

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, user equipment(UEs) 115, and a core network 130. In some examples, the wirelesscommunications system 100 may be a Long Term Evolution(LTE)/LTE-advanced (LTE-a) network.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude uplink (UL) transmissions from a UE 115 to a base station 105,or downlink (DL) transmissions, from a base station 105 to a UE 115. UEs115 may be dispersed throughout the wireless communications system 100,and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile station, a subscriber station, a remote unit, awireless device, an access terminal, a handset, a user agent, a client,or some other suitable terminology. A UE 115 may also be a cellularphone, a wireless modem, a handheld device, a personal computer, atablet, a personal electronic device, a machine type communication (MTC)device or the like.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., S1, etc.). Base stations105 may communicate with one another over backhaul links 134 (e.g., X2,etc.) either directly or indirectly (e.g., through core network 130).Base stations 105 may perform radio configuration and scheduling forcommunication with UEs 115, or may operate under the control of a basestation controller (not shown). In some examples, base stations 105 maybe macro cells, small cells, hot spots, or the like. Base stations 105may also be referred to as eNodeBs (eNBs) 105.

Wireless communication links 145 may also be established between UEs115, and between UEs 115 and relays 135, in a configuration known as D2Dcommunications. D2D communication directly between two UEs 115 may bereferred to as one-hop D2D communication. D2D communication between twoUEs 115 through a relay 135 may be referred to as two-hop D2Dcommunication. In some cases, a relay 135 may be an idle UE 115 (or a UE115 that otherwise has the resources, and capacity, to serve as arelay). In some cases, a relay 135 may be a base station 105, such as asmall cell. One or more of a group of UEs 115 utilizing D2Dcommunications may be within the coverage area 110 of a cell. Other UEs115 in such a group may be outside the coverage area 110 of a cell, orotherwise unable to receive transmissions from a base station 105. Insome cases, groups of UEs 115 communicating via D2D communications mayutilize a one-to-many (1:M) system in which each UE 115 transmits toevery other UE 115 in the group. In some cases, a base station 105 or arelay 135 facilitates the scheduling of resources for D2Dcommunications. In other cases, D2D communications are carried outindependent of a base station 105 or a relay 135.

HARQ may be a method of ensuring that data is received correctly over awireless communication link 125. hybrid automatic repeat request (HARQ)may include a combination of error detection (e.g., using a cyclicredundancy check (CRC)), forward error correction (FEC), andretransmission (e.g., automatic repeat request (ARQ)). HARQ may improvethroughput at the medium access control (MAC) layer in poor radioconditions (e.g., signal-to-noise conditions). In Incremental RedundancyHARQ, incorrectly received data may be stored in a buffer and combinedwith subsequent transmissions to improve the overall likelihood ofsuccessfully decoding the data. In some cases, redundancy bits are addedto each message prior to transmission. This may be especially useful inpoor conditions. In other cases, redundancy bits are not added to eachtransmission, but are retransmitted after the transmitter of theoriginal message receives a NACK indicating a failed attempt to decodethe information. The chain of transmission, response and retransmissionmay be referred to as a HARQ process. In some cases, a limited number ofHARQ processes may be used for a given communication link 125.

In some cases, a UE 115 (or a base station 105) may be detectable by acentral base station 105, but not by other UEs 115 in the coverage area110 of the central base station 105. For example, one UE 115 may be atone end of the coverage area 110 of the central base station 105 whileanother UE 115 may be at the other end. Thus, both UEs 115 maycommunicate with the base station 105, but may not receive thetransmissions of the other. This may result in colliding transmissionsfor the two UEs 115 in a contention based environment (e.g., D2Dcommunications) because the UEs 115 may not refrain from transmitting ontop of each other. A UE 115 whose transmissions are not identifiable,but that is within the same coverage area 110 may be known as a hiddennode. D2D environments may be supplemented by the exchange of a RTSpacket transmitted by a sending UE 115 (or base station 105) and a CTSpacket transmitted by the receiving UE 115 (or base station 105). Thismay alert other devices within range of the sender and receiver not totransmit for the duration of the primary transmission. Thus, RTS/CTS mayhelp mitigate a hidden node problem or prevent collisions.

It may be useful to establish a relay 135 between two UEs 115. Further,it may be beneficial if the relay 135 initiates the relationship, as itmay allow the UEs 115 to conserve power or more efficiently communicate(e.g., because the UEs may reduce time spent trying to find a relay135). As such, a relay 135 may monitor communications (e.g., D2Dcommunications between UEs 115) within a range, or communicationsdetectable by the relay 135. In some cases, the relay 135 may monitorcommunications between a number of D2D UE 115 pairs. The relay 135 maydetermine a UE 115 pair for which to facilitate communications. In somecases, the determined UE 115 pair may be a pair of UEs 115 which areexchanging NACKs, or a pair of UEs 115 which the introduction of therelay 135 may benefit. The relay 135 may determine to facilitatecommunications between a pair of UEs 115 which may benefit the mostamong the D2D communications which the relay 135 may detect. The relay135 may detect a first transmission from a first UE 115 of the pair ofUEs 115 to a second UE 115 of the pair of UEs 115, and may transmit amessage to the second UE 115 which may contain at least some of theinformation of the first transmission from the first UE 115. The secondUE 115 may transmit a response, responsive to the first transmission,which may be received by the relay 135. The relay 135 may transmitinformation relating to the relay 135 to the second UE 115. The secondUE 115 may transmit the information relating to the relay 135 to thefirst UE 115. The first UE 115 and second UE 115 may communicatethrough, or using, the relay 135.

FIG. 2 illustrates an example of a wireless communications subsystem 200for introduction of powered relay for D2D communication in accordancewith various aspects of the present disclosure. Wireless communicationssubsystem 200 may include UEs 115 which may be examples of a UE 115 asdescribed with reference to FIG. 1. Wireless communications subsystem200 may include relay 135-a, which may be an example of a UE 115, a basestation 105, or a relay 135 as described with reference to FIG. 1.

A relay 135-a may monitor 205 communications 145-a between UEs 115. Therelay 135-a may be a PGC relay, or may have lenient power restrictions.For example, the relay 135-a may be able to freely, or constantly,monitor communication links 145-a. The UEs 115 may have a linkestablished with another UE 115 and may be communicating using D2Dcommunications. The relay 135-a may monitor 205 communications 145-awhich the relay 135-a can detect, or are within a range. In some cases,the relay 135-a may monitor 205 a number of communications 145-a, or anumber of links. The relay 135-a, or another network device, maydetermine a link for which to attempt to facilitate communications, orhelp. The relay 135-a may help a single link, or multiple links.Determining which link to help may be based on a signal strength, themessages exchanged, or other factors. For example, the relay 135-a maymonitor 205 RTS, CTS, ACK, and NACK messages. A link with a greaternumber of NACKs may be an ideal link to attempt to help, as messages arenot always properly transmitted between the UEs 115.

The relay 135-a may determine to help the link between UE 115-b and UE115-c. The relay 135-a may monitor 205 communications 145-a between UE115-b and UE 115-c. The relay 135-a may identify a message, such as amessage transmitted from a first UE 115-b directed to a second UE 115-c.In some cases, the message may be an RTS. The relay 135-a may transmit amessage to the second UE 115-c. In some cases, the message transmittedfrom the relay 135-a to the second UE 115-c may contain some or all ofthe information contained in the message or characteristics of themessage transmitted from the first UE 115-b and directed to the secondUE 115-c. Further, the message transmitted from the relay 135-a may betransmitted on the same set of resources (e.g., frequency channel, timeslot, coding rate, modulation and coding scheme (MCS), etc.) as themessage transmitted from the first UE 115-b. For example, the relay135-a may transmit an RTS to the second UE 115-c. In some cases, themessage transmitted from the relay 135-a to the second UE 115-c may betransmitted using a power which is equal to, or similar to, the powerused when transmitting the message from the first UE 115-b to the secondUE 115-c. At times, the message transmitted by the first UE 115-b andthe message transmitted by the relay 135-a, may be received atapproximately the same time, or a similar time, by the second UE 115-c.

The second UE 115-c may transmit a response, which may be responsive toat least one of the message transmitted from the first UE 115-b and themessage transmitted from the relay 135-a. If the relay 135-a is locatedcloser to the second UE 115-c than is the first UE 115-b, the messagefrom the relay 135-a may be received at the second UE 115-c with ahigher power than the message from the first UE 115-b. At times, thepower of the response may be inversely proportional to the power of thereceived message(s), such as based on an inverse power echo mechanism.As such, the power of the response transmitted from the second UE 115-cmay be based on the power of the message received from the relay 135-a.The response may be received by the relay 135-a. At times, the first UE115-b may not receive the response from the second UE 115-c (e.g., dueto higher pathloss or insufficient transmit power). The response mayinclude a CTS or ACK. If the response is received at the first UE 115-b,the first UE 115-b and the second UE 115-c may continue D2Dcommunications, such as without use of the relay 135-a. Further, ifneither the first UE 115-b nor the relay 135-a receive the response, thefirst UE 115-b and the second UE 115-c may continue D2D communications,such as without use of the relay 135-a.

If the relay 135-a receives the response from the second UE 115-c, therelay 135-a may transmit data to be received at the second UE 115-c. Thedata may include information associated with the relay 135-a, or use ofthe relay 135-a, such as an identification (e.g., 16 bit identifier, 64bit identifier, etc.) of the relay, a coding rate, a MCS, or otherinformation associated with the relay 135-a, or use of the relay 135-a.The data may be coded at a low rate (e.g., 1/10 or less) to allowreliable decoding. In some cases, decoding overhead may be reduced ifthe relay 135-a uses the same MCS for transmission of the data as thefirst UE 115-b previously used for transmissions to the second UE 115-c.

The second UE 115-c may detect if the data was received from the firstUE 115-b or the relay 135-a. If the data is properly received at thesecond UE 115-c from the relay 135-a, the second UE 115-c may detect thedata and acknowledge reception (e.g., transmit an ACK to the relay135-a). Otherwise, the second UE 115-c may transmit a NACK to the relay135-a or continue normal D2D communications with the first UE 115-b.ACKs or NACKs may have different bit patterns, such as depending onwhether it is transmitted to the first UE 115-b or the relay 135-a. Therelay 135-a may continue to mimic portions of transmissions between thefirst UE 115-b and the second UE 115-c as described above, or other D2Dpairs, until the relay 135-a receives an ACK from a UE 115, such as thesecond UE 115-c.

The second UE 115-c may transmit a message to the first UE 115-b. Themessage may be an RTS. The message may further include informationrelating to the relay 135-a, such as information needed for the D2D pairto operate through the relay 135-a. As discussed above, the informationmay include an identification of the relay 135-a, an MCS, etc. Themessage transmitted from the second UE 115-c may inform the first UE115-b of the presence of the relay 135-a. At times, higher-layerauthentication may be performed, allowing the D2D pair to operate usingthe relay 135-a.

The relay 135-a may facilitate communications between the first UE 115-band the second UE 115-c, such as using communication link 145-b andcommunication link 145-c. Facilitating communications may include therelay 135-a interacting with both the first UE 115-b and the second UE115-c. For example, the first UE 115-b may transmit a message intendedfor the second UE 115-c, to the relay 135-a. The relay 135-a may thentransmit the message from the first UE 115-b to the second UE 115-c.Further, the second UE 115-c may transmit a message intended for thefirst UE 115-b to the relay 135-a. The relay 135-a may then transmit themessage from the second UE 115-c to the first UE 115-b.

The relay 135-a may facilitate communications for a number of D2D pairs,such as simultaneously or subsequently. Further, the relay 135-a maycontinue to monitor other D2D links 145-a while facilitatingcommunications for a D2D link. At times, the relay 135-a may transitionto facilitating communications for another D2D pair, such as if it isdetermined that the other D2D pair would benefit from the relay 135-afacilitating communications more than the currently assisted D2D pair.In some cases, the relay 135-a may communicate with a base station 105or another relay 135. Further, the relay 135-a may coordinatecommunications between the D2D pair based on information obtained fromthe base station.

FIG. 3 illustrates an example of a process flow 300 for introduction ofpowered relay for D2D communication in accordance with various aspectsof the present disclosure. Process flow 300 may include UE 115-d and UE115-e, which may be examples of UEs 115 described with reference toFIGS. 1-2. Process flow 300 may include relay 135-b, which may be anexample of a UE 115, a base station 105, or a relay 135 described withreference to FIGS. 1-2.

At block 305, a D2D communication link is established between a firstdevice 115-d and a second device 115-e.

At block 310, the first device 115-d may transmit a first message to thesecond device 115-e. In some examples the first message is an RTSmessage.

At block 315, the relay 135-b may identify, at a relay device, the firstmessage transmitted from the first device 115-d directed to the seconddevice 115-e using D2D communications on a first set of resources. Therelay 135-b may identify, at the relay device, a set of D2D messagesassociated with a set of D2D device pairs. The relay 135-b may attemptto facilitate communications between the first device 115-d and thesecond device 115-e based on the first message, or the set of D2Dmessages, or a combination thereof. In some examples the relay device135-b is connected to a power grid. In some examples the first set ofresources comprises a frequency channel, or a time slot, or a codingrate, or a MCS, or a combination thereof.

At block 320, the relay 135-b may transmit a second message to thesecond device 115-e on the first set of resources upon identifying thetransmission of the first message, the second message including at leasta portion of the first message. The relay 135-b may transmit the secondmessage to the second device 115-e at a power level that may be equal toa power level used to transmit the first message to the second device115-e.

At block 325, the relay 135-b may receive a response to the secondmessage from the second device 115-e. In some examples the response is aCTS message. In some examples the response is an ACK.

At block 330, the relay 135-b may transmit information associated withthe relay device 135-b to the second device 115-e, the informationincluding an identification of the relay device 135-b, or a modulationand coding scheme (MCS), or a combination thereof.

At block 335, the second device 115-e may transmit the informationassociated with the relay 135-b to the first device 115-d.

At block 340, the relay 135-b may facilitate communications between thefirst device 115-d and the second device 115-e. In some examplesfacilitating communications comprises: at least one of receiving a thirdmessage from the first device 115-d and retransmitting the third messageto the second device 115-e and receiving a fourth message from thesecond device 115-e and retransmitting the fourth message to the firstdevice 115-d. Facilitating communications between the first device 115-dand the second device 115-e may be initiated by the relay device 135-b.

FIG. 4 shows a block diagram of a wireless device 400 configured forintroduction of powered relay for D2D communication in accordance withvarious aspects of the present disclosure. Wireless device 400 may be anexample of aspects of a UE 115, a relay 135, or a base station 105described with reference to FIGS. 1-3. Wireless device 400 may include areceiver 405, a relay management module 410, or a transmitter 415.Wireless device 400 may also include a processor. Each of thesecomponents may be in communication with each other.

The receiver 405 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to introductionof powered relay for D2D communication, etc.). Information may be passedon to the relay management module 410, and to other components ofwireless device 400.

The relay management module 410 may identify, at a relay device, a firstmessage transmitted from a first device directed to a second deviceusing D2D communications on a first set of resources, transmit a secondmessage to the second device on the first set of resources uponidentifying the transmission of the first message, the second messagecomprising at least a portion of the first message, and receive aresponse to the second message from the second device.

The transmitter 415 may transmit signals received from other componentsof wireless device 400. In some examples, the transmitter 415 may becollocated with the receiver 405 in a transceiver module. Thetransmitter 415 may include a single antenna, or it may include aplurality of antennas.

FIG. 5 shows a block diagram of a wireless device 500 for introductionof powered relay for D2D communication in accordance with variousaspects of the present disclosure. Wireless device 500 may be an exampleof aspects of a wireless device 400, a UE 115, a relay 135, or a basestation 105 described with reference to FIGS. 1-4. Wireless device 500may include a receiver 405-a, a relay management module 410-a, or atransmitter 415-a. Wireless device 500 may also include a processor.Each of these components may be in communication with each other. Therelay management module 410-a may also include a link identificationmodule 505, and a relay initiation module 510.

The receiver 405-a may receive information which may be passed on torelay management module 410-a, and to other components of wirelessdevice 500. The relay management module 410-a may perform the operationsdescribed with reference to FIG. 4. The transmitter 415-a may transmitsignals received from other components of wireless device 500.

The link identification module 505 may identify, at a relay device, afirst message transmitted from a first device directed to a seconddevice using D2D communications on a first set of resources as describedwith reference to FIGS. 2-3. The link identification module 505 may alsoidentify, at the relay device, a plurality of D2D messages associatedwith a plurality of D2D device pairs. In some examples, a D2Dcommunication link may be established between the first device and thesecond device. In some examples, the first message may be a RTS message.

The relay initiation module 510 may transmit a second message to thesecond device on the first set of resources upon identifying thetransmission of the first message, the second message comprising atleast a portion of the first message as described with reference toFIGS. 2-3. The relay initiation module 510 may also receive a responseto the second message from the second device. The relay initiationmodule 510 may also transmit the second message to the second device ata power level that is equal to a power level used to transmit the firstmessage to the second device. The relay initiation module 510 may alsotransmit information associated with the relay device to the seconddevice, the information comprising an identification of the relaydevice, or a MCS, or a combination thereof. In some examples, the relaydevice may be connected to a power grid. In some examples, the responsemay be a CTS message. In some examples, the response may be an ACK. Insome examples, the first set of resources comprises a frequency channel,or a time slot, or a coding rate, or a MCS, or a combination thereof.

FIG. 6 shows a block diagram 600 of a relay management module 410-bwhich may be a component of a wireless device 400 or a wireless device500 for introduction of powered relay for D2D communication inaccordance with various aspects of the present disclosure. The relaymanagement module 410-b may be an example of aspects of a relaymanagement module 410 described with reference to FIGS. 4-5. The relaymanagement module 410-b may include a link identification module 505-a,and a relay initiation module 510-a. Each of these modules may performthe functions described with reference to FIG. 5. The relay managementmodule 410-b may also include a communication facilitation module 605,and a link selection module 610.

The communication facilitation module 605 may facilitate communicationsbetween the first device and the second device as described withreference to FIGS. 2-3. In some examples, facilitating communicationscomprises at least one of receiving a third message from the firstdevice and retransmitting the third message to the second device. Thecommunication facilitation module 605 may also receive a fourth messagefrom the second device and retransmitting the fourth message to thefirst device. The communication facilitation module 605 may alsofacilitate communications between the first device and the second deviceis initiated by the relay device.

The link selection module 610 may attempt to facilitate communicationsbetween the first device and the second device based at least in part onthe first message, or the plurality of D2D messages, or a combinationthereof as described with reference to FIGS. 2-3.

FIG. 7 shows a diagram of a system 700 including a relay 135 configuredfor introduction of powered relay for D2D communication in accordancewith various aspects of the present disclosure. System 700 may includerelay 135-b, which may be an example of a wireless device 400, awireless device 500, a UE 115, a relay 135, or a base station 105described with reference to FIGS. 1-6. Relay 135-b may include a relaymanagement module 710, which may be an example of a relay managementmodule 410 described with reference to FIGS. 4-6. Relay 135-b may alsoinclude components for bi-directional voice and data communicationsincluding components for transmitting communications and components forreceiving communications. For example, relay 135-b may communicatebi-directionally with base station 105-a or UE 115-f.

Relay 135-b may also include a processor 705, and memory 715 (includingsoftware (SW)) 720, a transceiver 735, and one or more antenna(s) 740,each of which may communicate, directly or indirectly, with one another(e.g., via buses 745). The transceiver 735 may communicatebi-directionally, via the antenna(s) 740 or wired or wireless links,with one or more networks, as described above. For example, thetransceiver 735 may communicate bi-directionally with a base station 105or a UE 115. The transceiver 735 may include a modem to modulate thepackets and provide the modulated packets to the antenna(s) 740 fortransmission, and to demodulate packets received from the antenna(s)740. While relay 135-b may include a single antenna 740, relay 135-b mayalso have multiple antennas 740 capable of concurrently transmitting orreceiving multiple wireless transmissions.

The memory 715 may include random access memory (RAM) and read onlymemory (ROM). The memory 715 may store computer-readable,computer-executable software/firmware code 720 including instructionsthat, when executed, cause the processor 705 to perform variousfunctions described herein (e.g., introduction of powered relay for D2Dcommunication, etc.). Alternatively, the software/firmware code 720 maynot be directly executable by the processor 705 but cause a computer(e.g., when compiled and executed) to perform functions describedherein. The processor 705 may include an intelligent hardware device,(e.g., a central processing unit (CPU), a microcontroller, anapplication specific integrated circuit (ASIC), etc.)

The components of wireless device 400, wireless device 500, relaymanagement module 410, and relay management module 710 may, individuallyor collectively, be implemented with at least one ASIC adapted toperform some or all of the applicable functions in hardware.Alternatively, the functions may be performed by one or more otherprocessing units (or cores), on at least one IC. In other examples,other types of integrated circuits may be used (e.g.,Structured/Platform ASICs, a field programmable gate array (FPGA), oranother semi-custom IC), which may be programmed in any manner known inthe art. The functions of each unit may also be implemented, in whole orin part, with instructions embodied in a memory, formatted to beexecuted by one or more general or application-specific processors.

FIG. 8 shows a flowchart illustrating a method 800 for introduction ofpowered relay for D2D communication in accordance with various aspectsof the present disclosure. The operations of method 800 may beimplemented by a relay 135 or its components as described with referenceto FIGS. 1-7. For example, the operations of method 800 may be performedby the relay management module 410 as described with reference to FIGS.4-7. In some examples, a relay 135 may execute a set of codes to controlthe functional elements of the relay 135 to perform the functionsdescribed below. Additionally or alternatively, the relay 135 mayperform aspects the functions described below using special-purposehardware.

At block 805, the relay 135 may identify, at a relay device, a firstmessage transmitted from a first device directed to a second deviceusing D2D communications on a first set of resources as described withreference to FIGS. 2-3. In certain examples, the operations of block 805may be performed by the link identification module 505 as described withreference to FIGS. 5 and 6.

At block 810, the relay 135 may transmit a second message to the seconddevice on the first set of resources upon identifying the transmissionof the first message, the second message comprising at least a portionof the first message as described with reference to FIGS. 2-3. Incertain examples, the operations of block 810 may be performed by therelay initiation module 510 as described with reference to FIGS. 5 and6.

At block 815, the relay 135 may receive a response to the second messagefrom the second device as described with reference to FIGS. 2-3. Incertain examples, the operations of block 815 may be performed by therelay initiation module 510 as described with reference to FIGS. 5 and6.

FIG. 9 shows a flowchart illustrating a method 900 for introduction ofpowered relay for D2D communication in accordance with various aspectsof the present disclosure. The operations of method 900 may beimplemented by a relay 135 or its components as described with referenceto FIGS. 1-7. For example, the operations of method 900 may be performedby the relay management module 410 as described with reference to FIGS.4-7. In some examples, a relay 135 may execute a set of codes to controlthe functional elements of the relay 135 to perform the functionsdescribed below. Additionally or alternatively, the relay 135 mayperform aspects the functions described below using special-purposehardware. The method 900 may also incorporate aspects of method 800 ofFIG. 8.

At block 905, the relay 135 may identify, at a relay device, a firstmessage transmitted from a first device directed to a second deviceusing D2D communications on a first set of resources as described withreference to FIGS. 2-3. In certain examples, the operations of block 905may be performed by the link identification module 505 as described withreference to FIGS. 5 and 6.

At block 910, the relay 135 may transmit a second message to the seconddevice on the first set of resources upon identifying the transmissionof the first message, the second message comprising at least a portionof the first message as described with reference to FIGS. 2-3. Incertain examples, the operations of block 910 may be performed by therelay initiation module 510 as described with reference to FIGS. 5 and6.

At block 915, the relay 135 may receive a response to the second messagefrom the second device as described with reference to FIGS. 2-3. Incertain examples, the operations of block 915 may be performed by therelay initiation module 510 as described with reference to FIGS. 5 and6.

At block 920, the relay 135 may facilitate communications between thefirst device and the second device as described with reference to FIGS.2-3. In certain examples, the operations of block 920 may be performedby the communication facilitation module 605 as described with referenceto FIG. 6.

FIG. 10 shows a flowchart illustrating a method 1000 for introduction ofpowered relay for D2D communication in accordance with various aspectsof the present disclosure. The operations of method 1000 may beimplemented by a relay 135 or its components as described with referenceto FIGS. 1-7. For example, the operations of method 1000 may beperformed by the relay management module 410 as described with referenceto FIGS. 4-7. In some examples, a relay 135 may execute a set of codesto control the functional elements of the relay 135 to perform thefunctions described below. Additionally or alternatively, the relay 135may perform aspects the functions described below using special-purposehardware. The method 1000 may also incorporate aspects of methods 800,and 900 of FIGS. 8-9.

At block 1005, the relay 135 may identify, at the relay device, aplurality of D2D messages associated with a plurality of D2D devicepairs as described with reference to FIGS. 2-3. In certain examples, theoperations of block 1005 may be performed by the link identificationmodule 505 as described with reference to FIGS. 5 and 6.

At block 1010, the relay 135 may identify, at a relay device, a firstmessage transmitted from a first device directed to a second deviceusing D2D communications on a first set of resources as described withreference to FIGS. 2-3. In certain examples, the operations of block1010 may be performed by the link identification module 505 as describedwith reference to FIGS. 5 and 6.

At block 1015, the relay 135 may attempt to facilitate communicationsbetween the first device and the second device based at least in part onthe first message, or the plurality of D2D messages, or a combinationthereof as described with reference to FIGS. 2-3. In certain examples,the operations of block 1015 may be performed by the link selectionmodule 610 as described with reference to FIG. 6.

At block 1020, the relay 135 may transmit a second message to the seconddevice on the first set of resources upon identifying the transmissionof the first message, the second message comprising at least a portionof the first message as described with reference to FIGS. 2-3. Incertain examples, the operations of block 1020 may be performed by therelay initiation module 510 as described with reference to FIGS. 5 and6.

At block 1025, the relay 135 may receive a response to the secondmessage from the second device as described with reference to FIGS. 2-3.In certain examples, the operations of block 1025 may be performed bythe relay initiation module 510 as described with reference to FIGS. 5and 6.

FIG. 11 shows a flowchart illustrating a method 1100 for introduction ofpowered relay for D2D communication in accordance with various aspectsof the present disclosure. The operations of method 1100 may beimplemented by a relay 135 or its components as described with referenceto FIGS. 1-7. For example, the operations of method 1100 may beperformed by the relay management module 410 as described with referenceto FIGS. 4-7. In some examples, a relay 135 may execute a set of codesto control the functional elements of the relay 135 to perform thefunctions described below. Additionally or alternatively, the relay 135may perform aspects the functions described below using special-purposehardware. The method 1100 may also incorporate aspects of methods 800,900, and 1000 of FIGS. 8-10.

At block 1105, the relay 135 may identify, at a relay device, a firstmessage transmitted from a first device directed to a second deviceusing D2D communications on a first set of resources as described withreference to FIGS. 2-3. In certain examples, the operations of block1105 may be performed by the link identification module 505 as describedwith reference to FIGS. 5 and 6.

At block 1110, the relay 135 may transmit a second message to the seconddevice on the first set of resources upon identifying the transmissionof the first message, the second message comprising at least a portionof the first message as described with reference to FIGS. 2-3. Incertain examples, the operations of block 1110 may be performed by therelay initiation module 510 as described with reference to FIGS. 5 and6.

At block 1115, the relay 135 may receive a response to the secondmessage from the second device as described with reference to FIGS. 2-3.In certain examples, the operations of block 1115 may be performed bythe relay initiation module 510 as described with reference to FIGS. 5and 6.

At block 1120, the relay 135 may transmit information associated withthe relay device to the second device, the information comprising anidentification of the relay device, or a MCS, or a combination thereofas described with reference to FIGS. 2-3. In certain examples, theoperations of block 1120 may be performed by the relay initiation module510 as described with reference to FIGS. 5 and 6.

Thus, methods 800, 900, 1000, and 1100 may provide for introduction ofpowered relay for D2D communication. It should be noted that methods800, 900, 1000, and 1100 describe possible implementation, and that theoperations and the steps may be rearranged or otherwise modified suchthat other implementations are possible. In some examples, aspects fromtwo or more of the methods 800, 900, 1000, and 1100 may be combined.

The description herein provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate.Also, features described with respect to some examples may be combinedin other examples.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.The terms “system” and “network” are often used interchangeably. A codedivision multiple access (CDMA) system may implement a radio technologysuch as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc.CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0and A are commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856)is commonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data(HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants ofCDMA. A time division multiple access (TDMA) system may implement aradio technology such as Global System for Mobile Communications (GSM).An orthogonal frequency division multiple access (OFDMA) system mayimplement a radio technology such as Ultra Mobile Broadband (UMB),Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications system (UMTS). 3GPP Long Term Evolution (LTE) andLong Term Evolution (LTE)-advanced (LTE-a) are new releases of UniversalMobile Telecommunications System (UMTS) that use E-UTRA. UTRA, E-UTRA,Universal Mobile Telecommunications System (UMTS), LTE, LTE-a, andGlobal System for Mobile communications (GSM) are described in documentsfrom an organization named “3rd Generation Partnership Project” (3GPP).CDMA2000 and UMB are described in documents from an organization named“3rd Generation Partnership Project 2” (3GPP2). The techniques describedherein may be used for the systems and radio technologies mentionedabove as well as other systems and radio technologies. The descriptionherein, however, describes an LTE system for purposes of example, andLTE terminology is used in much of the description above, although thetechniques are applicable beyond LTE applications.

In LTE/LTE-a networks, including such networks described herein, theterm evolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-a network in which different typesof evolved node B (eNBs) provide coverage for various geographicalregions. For example, each eNB or base station may provide communicationcoverage for a macro cell, a small cell, or other types of cell. Theterm “cell” is a 3GPP term that can be used to describe a base station,a carrier or component carrier associated with a base station, or acoverage area (e.g., sector, etc.) of a carrier or base station,depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an accesspoint, a radio transceiver, a NodeB, eNodeB (eNB), Home NodeB, a HomeeNodeB, or some other suitable terminology. The geographic coverage areafor a base station may be divided into sectors making up only a portionof the coverage area. The wireless communications system or systemsdescribed herein may include base stations of different types (e.g.,macro or small cell base stations). The UEs described herein may be ableto communicate with various types of base stations and network equipmentincluding macro eNBs, small cell eNBs, relay base stations, and thelike. There may be overlapping geographic coverage areas for differenttechnologies.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base station, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers). A UE may be able to communicate with varioustypes of base stations and network equipment including macro eNBs, smallcell eNBs, relay base stations, and the like.

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The downlink transmissions described herein may also be called forwardlink transmissions while the uplink transmissions may also be calledreverse link transmissions. Each communication link describedherein—including, for example, wireless communications system 100 and200 of FIGS. 1 and 2—may include one or more carriers, where eachcarrier may be a signal made up of multiple sub-carriers (e.g., waveformsignals of different frequencies). Each modulated signal may be sent ona different sub-carrier and may carry control information (e.g.,reference signals, control channels, etc.), overhead information, userdata, etc. The communication links described herein (e.g., communicationlinks 125 or D2D links 145 of FIG. 1) may transmit bidirectionalcommunications using frequency division duplex (FDD) (e.g., using pairedspectrum resources) or time division duplex (TDD) operation (e.g., usingunpaired spectrum resources). Frame structures may be defined forfrequency division duplex (FDD) (e.g., frame structure type 1) and TDD(e.g., frame structure type 2).

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), an ASIC, anFPGA or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, or any combination thereof designedto perform the functions described herein. A general-purpose processormay be a microprocessor, but in the alternative, the processor may beany conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices (e.g., a combination of a digital signal processor(DSP) and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of at least one of A, B, or C meansA or B or C or AB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media cancomprise RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave are included in the definition of medium. Disk and disc,as used herein, include CD, laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notto be limited to the examples and designs described herein but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method of wireless communication, comprising:identifying, at a relay device, a first message transmitted from a firstdevice directed to a second device using device-to-device (D2D)communications on a first set of resources; transmitting a secondmessage to the second device on the first set of resources uponidentifying the transmission of the first message, the second messagecomprising at least a portion of the first message; and receiving aresponse to the second message from the second device.
 2. The method ofclaim 1, further comprising: transmitting the second message to thesecond device at a power level that is equal to a power level used totransmit the first message to the second device.
 3. The method of claim1, further comprising: facilitating communications between the firstdevice and the second device.
 4. The method of claim 3, whereinfacilitating communications comprises at least one of: receiving a thirdmessage from the first device and retransmitting the third message tothe second device; and receiving a fourth message from the second deviceand retransmitting the fourth message to the first device.
 5. The methodof claim 3, wherein facilitating communications between the first deviceand the second device is initiated by the relay device.
 6. The method ofclaim 1, further comprising: identifying, at the relay device, aplurality of D2D messages associated with a plurality of D2D devicepairs; and attempting to facilitate communications between the firstdevice and the second device based at least in part on the firstmessage, or the plurality of D2D messages, or a combination thereof. 7.The method of claim 1, further comprising: transmitting informationassociated with the relay device to the second device, the informationcomprising an identification of the relay device, or a modulation andcoding scheme (MCS), or a combination thereof.
 8. The method of claim 1,wherein the relay device is connected to a power grid.
 9. The method ofclaim 1, wherein a D2D communication link is established between thefirst device and the second device.
 10. The method of claim 1, whereinthe first message is a request-to-send (RTS) message.
 11. The method ofclaim 10, wherein the response is a clear-to-send (CTS) message.
 12. Themethod of claim 1, wherein the response is an acknowledgment (ACK). 13.The method of claim 1, wherein the first set of resources comprises afrequency channel, or a time slot, or a coding rate, or a modulation andcoding scheme (MCS), or a combination thereof.
 14. An apparatus forwireless communication, comprising: means for identifying, at a relaydevice, a first message transmitted from a first device directed to asecond device using device-to-device (D2D) communications on a first setof resources; means for transmitting a second message to the seconddevice on the first set of resources upon identifying the transmissionof the first message, the second message comprising at least a portionof the first message; and means for receiving a response to the secondmessage from the second device.
 15. The apparatus of claim 14, furthercomprising: means for transmitting the second message to the seconddevice at a power level that is equal to a power level used to transmitthe first message to the second device.
 16. The apparatus of claim 14,further comprising: means for facilitating communications between thefirst device and the second device.
 17. The apparatus of claim 16,wherein the means for facilitating communications comprises at least oneof: means for receiving a third message from the first device andretransmitting the third message to the second device; and means forreceiving a fourth message from the second device and retransmitting thefourth message to the first device.
 18. The apparatus of claim 16,wherein facilitating communications between the first device and thesecond device is initiated by the relay device.
 19. The apparatus ofclaim 14, further comprising: means for identifying, at the relaydevice, a plurality of D2D messages associated with a plurality of D2Ddevice pairs; and means for attempting to facilitate communicationsbetween the first device and the second device based at least in part onthe first message, or the plurality of D2D messages, or a combinationthereof.
 20. The apparatus of claim 14, further comprising: means fortransmitting information associated with the relay device to the seconddevice, the information comprising an identification of the relaydevice, or a modulation and coding scheme (MCS), or a combinationthereof.
 21. The apparatus of claim 14, wherein the relay device isconnected to a power grid.
 22. The apparatus of claim 14, wherein a D2Dcommunication link is established between the first device and thesecond device.
 23. The apparatus of claim 14, wherein the first messageis a request-to-send (RTS) message.
 24. The apparatus of claim 23,wherein the response is a clear-to-send (CTS) message.
 25. The apparatusof claim 14, wherein the response is an acknowledgment (ACK).
 26. Theapparatus of claim 14, wherein the first set of resources comprises afrequency channel, or a time slot, or a coding rate, or a modulation andcoding scheme (MCS), or a combination thereof.
 27. An apparatus forwireless communication, comprising: a processor; memory in electroniccommunication with the processor; and instructions stored in the memoryand operable, when executed by the processor, to cause the apparatus to:identify, at a relay device, a first message transmitted from a firstdevice directed to a second device using device-to-device (D2D)communications on a first set of resources; transmit a second message tothe second device on the first set of resources upon identifying thetransmission of the first message, the second message comprising atleast a portion of the first message; and receive a response to thesecond message from the second device.
 28. The apparatus of claim 27,wherein the instructions are operable to cause the apparatus to:transmit the second message to the second device at a power level thatis equal to a power level used to transmit the first message to thesecond device.
 29. The apparatus of claim 27, wherein the instructionsare operable to cause the apparatus to: facilitate communicationsbetween the first device and the second device.
 30. The apparatus ofclaim 29, wherein facilitating communications comprises at least one of:receiving a third message from the first device and retransmitting thethird message to the second device; and receiving a fourth message fromthe second device and retransmitting the fourth message to the firstdevice.
 31. The apparatus of claim 29, wherein facilitatingcommunications between the first device and the second device isinitiated by the relay device.
 32. The apparatus of claim 27, whereinthe instructions are operable to cause the apparatus to: identify, atthe relay device, a plurality of D2D messages associated with aplurality of D2D device pairs; and attempt to facilitate communicationsbetween the first device and the second device based at least in part onthe first message, or the plurality of D2D messages, or a combinationthereof.
 33. The apparatus of claim 27, wherein the instructions areoperable to cause the apparatus to: transmit information associated withthe relay device to the second device, the information comprising anidentification of the relay device, or a modulation and coding scheme(MCS), or a combination thereof.
 34. The apparatus of claim 27, whereinthe relay device is connected to a power grid.
 35. The apparatus ofclaim 27, wherein a D2D communication link is established between thefirst device and the second device.
 36. The apparatus of claim 27,wherein the first message is a request-to-send (RTS) message.
 37. Theapparatus of claim 36, wherein the response is a clear-to-send (CTS)message.
 38. The apparatus of claim 27, wherein the response is anacknowledgment (ACK).
 39. The apparatus of claim 27, wherein the firstset of resources comprises a frequency channel, or a time slot, or acoding rate, or a modulation and coding scheme (MCS), or a combinationthereof.
 40. A non-transitory computer-readable medium storing code forwireless communication, the code comprising instructions executable to:identify, at a relay device, a first message transmitted from a firstdevice directed to a second device using device-to-device (D2D)communications on a first set of resources; transmit a second message tothe second device on the first set of resources upon identifying thetransmission of the first message, the second message comprising atleast a portion of the first message; and receive a response to thesecond message from the second device.
 41. The non-transitorycomputer-readable medium of claim 40, wherein the instructions areexecutable to: transmit the second message to the second device at apower level that is equal to a power level used to transmit the firstmessage to the second device.
 42. The non-transitory computer-readablemedium of claim 40, wherein the instructions are executable to:facilitate communications between the first device and the seconddevice.
 43. The non-transitory computer-readable medium of claim 42,wherein facilitating communications comprises at least one of: receivinga third message from the first device and retransmitting the thirdmessage to the second device; and receiving a fourth message from thesecond device and retransmitting the fourth message to the first device.44. The non-transitory computer-readable medium of claim 42, whereinfacilitating communications between the first device and the seconddevice is initiated by the relay device.
 45. The non-transitorycomputer-readable medium of claim 40, wherein the instructions areexecutable to: identify, at the relay device, a plurality of D2Dmessages associated with a plurality of D2D device pairs; and attempt tofacilitate communications between the first device and the second devicebased at least in part on the first message, or the plurality of D2Dmessages, or a combination thereof.
 46. The non-transitorycomputer-readable medium of claim 40, wherein the instructions areexecutable to: transmit information associated with the relay device tothe second device, the information comprising an identification of therelay device, or a modulation and coding scheme (MCS), or a combinationthereof.
 47. The non-transitory computer-readable medium of claim 40,wherein the relay device is connected to a power grid.
 48. Thenon-transitory computer-readable medium of claim 40, wherein a D2Dcommunication link is established between the first device and thesecond device.
 49. The non-transitory computer-readable medium of claim40, wherein the first message is a request-to-send (RTS) message. 50.The non-transitory computer-readable medium of claim 49, wherein theresponse is a clear-to-send (CTS) message.
 51. The non-transitorycomputer-readable medium of claim 40, wherein the response is anacknowledgment (ACK).
 52. The non-transitory computer-readable medium ofclaim 40, wherein the first set of resources comprises a frequencychannel, or a time slot, or a coding rate, or a modulation and codingscheme (MCS), or a combination thereof.